A tag is known which has an antenna and an IC chip, storing information about an article to be managed, electrically connected to the antenna, as a tag using the RFID technique. By transmitting radio waves at a predetermined frequency to the antenna from the transceiving antenna of an interrogator, the tag is activated, data is read from the IC chip in accordance with a read command through data communication by radio waves, and data is written in the IC chip in accordance with a write command. Moreover, a 1-bit RFID used for simplest EAS (Electronic Article Surveillance) is constituted by a capacitor and an antenna, which resonates by receiving a predetermined frequency and detects presence or absence of an article under surveillance.
In order to minimize the thickness of the tag, the above conventional antenna for RFID used for the tag uses an antenna formed by forming a conductive wire whose surface is covered with an insulating layer into a nearly squared spiral and attaching it to a base plate or an antenna which is spiral by removing unnecessary portions of a conductive layer formed by an aluminum foil or copper foil through etching or punching. In the case of a tag having the above antenna, when an article to be managed is made of a metal, the tag is affixed to the article by using a machine screw or the like while inserting a spacer having a thickness of 5 to 10 mm and electrical insulating properties between the tag and article in order to avoid the influences of the metallic article.
However, in the case of the above conventional tag, because the spacer has a relatively large thickness, the interval between the metallic article and tag becomes relatively large, even if the thickness of the antenna can be decreased, and a problem thereby occurs in that the tag greatly protrudes from the article to be managed. Therefore, the tag may contact a neighboring object while the article is being transported.
It is an object of the present invention to provide an antenna for RFID which can be directly affixed to an article to be managed, without using a spacer, no matter the kind of material making up the surface of the article.